The present invention relates to the formation of conductive structures. More particularly, the present invention pertains to deformation of one or more metal layers to form such conductive structures.
Various manners of fabricating a diverse and wide range of structures are available. Particularly, a wide variety of techniques are available for forming conductive structures of integrated circuits. For example, various photolithography and etching techniques are known, various methods of micromachining silicon devices is known, etc. However, there is always a need for additional novel approaches for forming such structures.
Dimensions in integrated circuits are constantly being reduced. For example, the separation between conductive layers is being reduced to achieve smaller integrated circuits. With a reduction in the spacing between conductive materials in an integrated circuit, an increase in capacitive crosstalk is observed. Conventional integrated circuits typically utilize interconnect structures wherein a first metal line is separated from a second metal line by an insulative material. If the capacitive effects between the first metal line and the second metal line is high, i.e., a voltage on one effects a voltage on the other, then the capacitive effects may lead to an inoperable integrated circuit.
To reduce such capacitive coupling or to provide isolation in integrated circuits, low dielectric constant materials have been utilized between such conductive materials or lines. However, use of low dielectric constant materials have many associated problems. For example, equipment is not always available to properly process new low dielectric materials in various integrated circuits. Further, for example, such dielectric materials may not properly or adequately reduce such capacitive coupling between the conductive materials.
A void region or space may also serve as a dielectric and offers the lowest possible dielectric constant, having a value equal to 1. It is noted that a void space can comprise a vacuum, but typically comprises some gases. A void space can alternatively be referred to as a free space, i.e., space that is empty of materials in a solid or liquid phase. It would be desirable to develop methods of forming void regions for use as low dielectric regions, such as for isolation in semiconductor constructions.
The present invention provides a method for forming a conductive structure, e.g., a conductive structure over a void region. The method involves controlled deformation and shaping of a metal layer employing a hydrogen gas source and thermal treatment of the source. The hydrogen gas source is preferably a hydrogen containing metal layer. Upon thermal heating, hydrogen gas evolves from the hydrogen containing metal layer and creates a pressure that exerts force sufficient to produce deformation in another metal layer. In other words, temperature, pressure and time along with differences in hydrogen solubility and diffusivity between different metal layers are used to form conductive structures. For example, release of hydrogen from a hydrogen containing metal layer is used to controllably deform an overlying metal layer.
For example, using the present invention, conductive metals can be shaped and/or supported over a void region. The present invention provides a method to prepare a diverse and wide range of structures that may be used for various applications, e.g., interconnections in integrated circuits, for transistor and packaging technologies, switching arrays, micromachined silicon devices, microchannels for fluid transport and bulk material deformation applications.
Accordingly, the present invention provides a method for forming a conductive structure by providing a substrate assembly having a surface. At least one hydrogen containing first metal layer (e.g., patterned or unpatterned layer) is formed on the substrate assembly surface. A second metal layer is formed on at least a portion of the first metal layer and at least the first metal layer is thermally treated to deform at least a portion of the second metal layer.
In one embodiment of the method, the method includes thermally treating at least the first metal layer to deform at least a portion of the second metal layer by a diffusion of hydrogen gas out of the hydrogen containing first metal layer. In another embodiment of the method, the formation of the at least one hydrogen containing first metal layer includes forming a layer of at least one high hydrogen solubility metal and incorporating hydrogen in the high hydrogen solubility metal layer. Preferably, the formation of the at least one hydrogen containing first metal layer includes forming a metal hydride layer.
Further, in other embodiments of the invention, the method provides incorporation of hydrogen into the high hydrogen solubility metal layer by diffusion through the second metal layer. Alternatively, the incorporation of hydrogen into the high hydrogen solubility metal layer is accomplished by exposing the high hydrogen solubility metal layer to a hydrogen atmosphere.
Preferably, the high hydrogen solubility metal employed in the method is at least one metal typically selected from the group of titanium, zirconium, thorium, hafnium, vanadium, niobium, tantalum, lanthanum, cerium, and palladium. Additionally, the high hydrogen solubility metal may have a hydrogen permeability of about 4 or more orders of magnitude greater than a hydrogen permeability of the low hydrogen solubility metal. Preferably, the low hydrogen solubility metal is at least one metal typically selected from the group of copper, silver, gold, tungsten, platinum, aluminum, molybdenum, iron and nickel.
The present invention further provides a method for forming a conductive structure by providing a substrate assembly having a surface; forming at least one hydrogen containing first metal layer on the substrate assembly surface; forming a second metal layer on at least a portion of the first metal layer; providing a clamping structure positioned over at least a portion of the second metal layer; and thermally treating at least the first metal layer to deform at least a portion of the second metal layer. In one embodiment of the method, the method includes providing a clamping structure positioned on at least a portion of a perimeter of the second metal layer. In another embodiment, the method also provides a mold, e.g., a heated mold, positioned over at least a portion of the second metal layer.
The invention also provides a method for forming a void region associated with a substrate assembly by providing a substrate assembly having a surface; forming at least one hydrogen containing first metal layer on the substrate assembly surface; forming a second metal layer on at least a portion of the first metal layer; and thermally treating at least the first metal layer to define a void between at least a portion of the substrate assembly surface and a portion of the second metal layer.
Also provided is a method for forming a conductive structure by providing a substrate assembly having a surface; forming at least one hydrogen containing first metal layer on at least a portion of the substrate assembly surface; oxidizing at least a portion of the at least one hydrogen containing first metal layer resulting in an oxidized layer; forming a second metal layer on at least a portion of the oxidized layer; and thermally treating at least the first metal layer to deform at least a portion of the second metal layer. For example, oxidizing at least a portion of the hydrogen containing first metal layer may result in an oxidized layer having a thickness of about 1 angstrom to about 20 angstroms.
In one embodiment of this method, the method further includes forming a carbon layer on at least a portion of the oxidized layer. For example, formation of the carbon layer typically results in a carbon layer having a thickness of about 1 angstrom to about 25 angstroms.
In another embodiment of the method, the method includes forming a seed metal layer of a low hydrogen solubility metal on the oxidized layer. The method may further include electrodepositing the low hydrogen solubility metal on the seed metal layer. Additionally, formation of the second metal layer may also include forming a seed metal layer of a low hydrogen solubility metal on the oxidized layer.
The invention also provides a conductive structure, wherein the conductive structure contains a substrate assembly having a surface; a high hydrogen solubility metal on at least a portion of the substrate assembly surface; and a raised conductive region comprising a low hydrogen solubility metal. At least a portion of the high hydrogen solubility metal and low hydrogen solubility metal are separated by a void region.